Antibiotics Mechanisms

Question 1

The Minimal Inhibitory Concentration (MIC) defines the minimum dose needed for an antimicrobial to do what?

Answer 1

Be bacteriostatic

Question 2

What is the most common mechanism by which antibiotics inhibit or kill bacteria?

Answer 2

Interference with cell wall synthesis

Question 3

What is the 2nd most common mechanism by which antibiotics inhibit or kill bacteria?

Answer 3

Interference with protein synthesis (targets the bacterial ribosome)

Question 4

What is a common mechanism by which antifungals work?

Answer 4

Inference with cytoplasmic (plasma) membrane function

Question 5

The bacterial cell wall is synthesized by cross-linking peptidoglycan strands using what enzymes?

Answer 5

Penicillin Binding Proteins (PBPs)

Question 6

State the mechanism of action and whether the agent is static or cidal: Penicillin

Answer 6

Interference with cell wall synthesis; bacteriocidal

Question 7

State the mechanism of action and whether the agent is static or cidal: Cephalosporins

Answer 7

Interference with cell wall synthesis; bacteriocidal

Question 8

State the mechanism of action and whether the agent is static or cidal: Glycopeptides / Vancomycin

Answer 8

Interference with cell wall synthesis; bacteriocidal

Question 9

State the mechanism of action and whether the agent is static or cidal: Macrolids

Answer 9

Interference with protein synthesis; bacteriostatic

Question 10

State the mechanism of action and whether the agent is static or cidal: Tetracyclines

Answer 10

Interference with protein synthesis; bacteriostatic

Question 11

State the mechanism of action and whether the agent is static or cidal: Fluoroquinolones

Answer 11

Interference with nucleic acid synthesis; bacteriocidal

Question 12

State the mechanism of action and whether the agent is static or cidal: Aminoglycosides

Answer 12

Interference with protein synthesis; bacteriocidal

Question 13

State the mechanism of action and whether the agent is static or cidal: Sulfonamides + Trimethoprim

Answer 13

Interference with metabolic pathways; bacteriocidal (sulfonamides are static, but trimethoprim is cidal so together they are cidal)

Question 14

What are the 4 classes of beta-lactam antibiotics?

Answer 14

Penicillins, cephalosporins, monobactams, carbapenems

Question 15

Name 3 advantages of beta-lactams.

Answer 15

Non-toxic, cheap, and mostly water-soluble

Question 16

Specifically, how does a beta-lactam inhibit cell wall synthesis?

Answer 16

It irreversibly inhibits the penicillin binding protein / transpeptidase by mimicking the D-Ala-D-Ala residues that would normally bind there

Question 17

Specifically, how does a glycopeptide inhibit cell wall synthesis?

Answer 17

It binds to the D-Ala-D-Ala residues of a peptidoglycan strand, thus preventing the strand from cross-linking

Question 18

Specifically, how does a macrolid inhibit protein synthesis?

Answer 18

It binds to the bacterial ribosome, blocking the exit of the growing peptide chain

Question 19

Specifically, how does a tetracycline inhibit protein synthesis?

Answer 19

It prevents the tRNA-aa complex from attaching to the ribosome

Question 20

Specifically, how does a fluoroquinolone inhibit nucleic acid synthesis?

Answer 20

It inhibits DNA gyrase and DNA topoisomerase

Question 21

Specifically, how does an aminoglycoside inhibit protein synthesis?

Answer 21

It changes the shape of the bacterial ribosome so that mRNA is read incorrectly

Question 22

Specifically, how do sulfamethoxazole and trimethoprim (often given together as TMP/SMX) interfere with metabolic pathways?

Answer 22

Sulfamethoxazole competes with PABA while trimethoprim inhibits DHF reductase, together preventing folic acid synthesis

Question 23

Ampicillin, amoxicillin, and piperacillin are examples of what class of beta-lactam?

Answer 23

Penicillin

Question 24

Cefotaxime, ceftriaxone, and cefipime are examples of what class of beta-lactam?

Answer 24

Cephalosporin

Question 25

Compared to 1st generation cephalosporins, do 3rd generation cephalosporins have better or worse activity against Gram(+) and Gram (-) bacteria?

Answer 25

3rd gen has better Gram (-) activity, worse Gram (+)

Question 26

Vancomycin is an example of what kind of cell wall inhibitor?

Answer 26

Glycopeptide

Question 27

Are glycopeptides and lipoglycopeptides more effective against Gram (+) or Gram (-) bacteria?

Answer 27

Gram(+) - they can’t get through the porins of Gram (-) bacteria to attack their cell walls

Question 28

Gentamycin, tobramycin, and amikacin are examples of what kind of protein synthesis inhibitor?

Answer 28

Aminoglycoside

Question 29

Erythromycin and azithromycin are examples of what kind of protein synthesis inhibitor?

Answer 29

Macrolid

Question 30

Ciprofloxacin, levofloxacin, and norfloxacin are examples of what kind of nucleic acid synthesis inhibitor?

Answer 30

Fluoroquinolone